freebmd.rootsweb.com shows Mar 1852 quarter marriages, William Vivian and Mary Jane 'Cornelias', Volume: 5c
Page: 393
district of Redruth.
I'd suggest getting the marriage, because then you will confirm father's name (and know his occupation), have an address to search for the 1851 census, and hopefully also confirm his age (as I've found age of people on death certificates, as well as other info, to often be anywhere from only vaguely inaccurate to wildly wrong).